There is no doubt that Service Oriented Architecture (SOA) is really taking off. Many large enterprises have investigated it, and have or will adopt it as a strategic direction, regardless of the underlying technology. As SOA is applied to more complex tasks, involving existing or legacy applications, there is a need for a repository to store metadata about enterprise information and services, as the basis for sophisticated discovery mechanisms. But can the Semantic Web provide a better alternative?

Integrated and Searchable Metadata Repository

Yefim Natis, vice president and distinguished analyst with Gartner, says that a metadata repository is a key enabling technology for SOA, and no long-term enterprise SOA initiative can succeed without an integrated and searchable repository or registry. SOA depends upon loosely coupled services with simple interfaces, and a discovery mechanism that enables consumers to find the services that they need.

In web-services there is a registry of descriptions expressed in the Web Services Description Language (WSDL) that can be queried using the Universal Description, Discovery, and Integration protocol (UDDI). As the more general concept of SOA evolves, many architects believe that this simple registry should be expanded to a sophisticated repository that includes content such as XML schemas and information metadata, as well as service descriptions.

An SOA repository stores and organizes metadata about services and the information that they consume and produce. It is used at design time by architects defining services and their inter-relationships, and by developers programming those services and the information transforms between them. It is used at run time by intelligent services searching for information sources. It improves programming productivity, increases re-use of software assets, and enables an intelligent architecture with dynamic connections between services. And, if metadata for existing applications is developed and included in the repository, it can liberate these applications’ data into the SOA world. With such a repository, SOA can open up the silos, and let the information flow.

There are SOA repository products on the market. According to Gartner, these range from simple registries focused on SOA software assets starting at around $50,000, to complex repositories focused on legacy modernization and understanding that may cost more than a million dollars. But there is another possible solution that could be freely available: the Semantic Web. Can this provide an open, interoperable, and low-cost discovery mechanism for SOA?